That certainly sounds wrong, but I'm having trouble reproducing your results. Our code is designed to hang on to all times in "Zulu" time, or Coordinated Universal Time, and they are formatted into the viewer's local time zone when viewed. My project's normal hours are 8-12, 1-5. When I suddenly appear on the grid in Valladolid, Spain, those times are translated to 5 PM - 9 PM, 10 PM - 2 AM. My resource's "8-5" off exception is similarly translated.
We should confirm what version of OmniPlan you're using, though. Can you possibly use the Help > Send Feedback option and send us a censored copy of your plan? Along with a description of the issue of course. The one you gave here seems perfectly adequate when paired with a sample document and OmniPlan version number.
Sorry for the trouble! It sounds as though this resource is entirely off for the week. Perhaps, assuming you're using version 2.0+, you could work around your problem by extending the off hours exception to cover the entire week, not just the working hours. It's perfectly ok for them to be oversized.